The objective of this research proposal is to explore the influence of modifying genes in the development of pulmonary hypertension (PAH) by identification of gene polymorphisms, measurement of their functional significance, and correlation of clinical data. Initial studies include the extraction, purification, and standardization of DNA from blood of patients with PAH, utilizing spectrophotometry, gel electrophoresis and real-time PCR. The genotyping and sequencing will be done using the TAQ-Man allelic discrimination assay or direct DNA sequencing. Once mutations and polymorphisms in candidate genes are discovered, the association of a genetic variation to a change in function will be investigated, initially utilizing immortalized, EBV-transformed, patient lymphoblastoid cell lines to quantifiy mRNA and perform cell function assays with tritium-labeled serotonin (5-HT) and a liquid scintillation counter. Correlation of genotype with patient phenotypic data, such as hemodynamic information, pharmacologic response, and survival, will be done utilizing the PAH database comprising both familial and sporadic patients. Statistical analysis will be performed using SPSS software, testing Kaplan-Meier curves, Chi-Square for associations of clinical features with genotypes, and T-test for discrete measures of difference between populations for single variables. [unreadable] [unreadable]